886 research outputs found
Human African trypanosomiasis : the current situation in endemic regions and the risks for non-endemic regions from imported cases
Human African trypanosomiasis (HAT) is caused by Trypanosoma brucei
gambiense and T. b. rhodesiense and caused devastating epidemics during the 20th
century. Due to effective control programs implemented in the last two decades, the
number of reported cases has fallen to a historically low level. Although fewer than
977 cases were reported in 2018 in endemic countries, HAT is still a public health
problem in endemic regions until it is completely eliminated. In addition, almost 150
confirmed HAT cases were reported in non-endemic countries in the last three
decades. The majority of non-endemic HAT cases were reported in Europe, United
States and South Africa, due to historical alliances, economic links or geographic
proximity to disease endemic countries. Furthermore, with the implementation of the
“Belt and Road” project, sporadic imported HAT cases have been reported in China
as a warning sign of tropical diseases prevention. In this paper, we explore and
interpret the data on HAT incidence and find no positive correlation between the
number of HAT cases from endemic and non-endemic countries.This data will
provide useful information for better understanding the imported cases of HAT
globally in the post-elimination phase
Vacuolar ATPase depletion contributes to dysregulation of endocytosis in bloodstream forms of Trypanosoma brucei
BACKGROUND
Vacuolar H-ATPase (V-ATPase) is a highly conserved protein complex which hydrolyzes ATP and pumps protons to acidify vacuolar vesicles. Beyond its role in pH maintenance, the involvement of V-ATPase in endocytosis is well documented in mammals and plants but is less clear in Trypanosoma brucei.
METHODS
In this study, the subcellular localization of V-ATPase subunit B (TbVAB) of T. brucei was assessed via in situ N-terminal YFP-tagging and immunofluorescence assays. Transgenic bloodstream forms (BSF) of T. brucei were generated which comprised either a V-ATPase subunit B (TbVAB) conditional knockout or a V-ATPase subunit A (TbVAA) knockdown. Acridine orange and BCECF-AM were employed to assess the roles of V-ATPase in the pH regulation of BSF T. brucei. The endocytic activities of three markers were also characterized by flow cytometry analyses. Furthermore, trypanosomes were counted from trypanolysis treatment groups (either containing 1% or 5% NHS) and endocytosed trypanosome lytic factor (TLF) was also analyzed by an immunoblotting assay.
RESULTS
TbVAB was found to localize to acidocalcisomes, lysosomes and probably also to endosomes of BSF of T. brucei and was demonstrated to be essential for cell growth. TbVAB depletion neutralized acidic organelles at 24 hours post-tetracycline depletion (hpd), meanwhile the steady state intracellular pH increased from 7.016 ± 0.013 to 7.422 ± 0.058. Trypanosomes with TbVAB depletion at 24 hpd were found to take up more transferrin (2.068 ± 0.277 fold) but less tomato lectin (49.31 ± 22.57%) by endocytosis, while no significant change was detected in dextran uptake. Similar endocytic dysregulated phenotypes were also observed in TbVAA knockdown cells. In addition, TbVAB depleted trypanosomes showed a low uptake of TLF and exhibited less sensitive to lysis in both 1% and 5% NHS treatments.
CONCLUSIONS
TbVAB is a key component of V-ATPase and was found to play a key function in endocytosis as well as exhibiting different effects in a receptor/cargo dependent manner in BSF of T. brucei. Besides vacuolar alkalinization, the dysregulation of endocytosis in TbVAB depleted T. brucei is considered to contribute to the reduced sensitivity to lysis by normal human serum
Polarized positron beams via intense two-color laser pulses
Generation of ultrarelativistic polarized positrons during interaction of an
ultrarelativistic electron beam with a counterpropagating two-color petawatt
laser pulse is investigated theoretically. Our Monte Carlo simulation based on
a semi-classical model, incorporates photon emissions and pair productions,
using spin-resolved quantum probabilities in the local constant field
approximation, and describes the polarization of electrons and positrons for
the pair production and photon emission processes, as well as the classical
spin precession in-between. The main reason of the polarization is shown to be
the spin-asymmetry of the pair production process in strong external fields,
combined with the asymmetry of the two-color laser field. Employing a feasible
scenario, we show that highly polarized positron beams, with a polarization
degree of , can be produced in a femtosecond time scale,
with a small angular divergence, mrad, and high density cm. The laser-driven positron source, along with laser
wakefield acceleration, may pave the way to small scale facilities for high
energy physics studies
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Design Principles for High-Capacity Mn-Based Cation-Disordered Rocksalt Cathodes
Mn-based Li-excess cation-disordered rocksalt (DRX) oxyfluorides are promising candidates for next-generation rechargeable battery cathodes owing to their large energy densities, the earth abundance, and low cost of Mn. In this work, we synthesized and electrochemically tested four representative compositions in the Li-Mn-O-F DRX chemical space with various Li and F content. While all compositions achieve higher than 200 mAh g−1 initial capacity and good cyclability, we show that the Li-site distribution plays a more important role than the metal-redox capacity in determining the initial capacity, whereas the metal-redox capacity is more closely related to the cyclability of the materials. We apply these insights and generate a capacity map of the Li-Mn-O-F chemical space, LixMn2-xO2-yFy (1.167 ≤ x ≤ 1.333, 0 ≤ y ≤ 0.667), which predicts both accessible Li capacity and Mn-redox capacity. This map allows the design of compounds that balance high capacity with good cyclability
Study on the construction workforce management based on lean construction in the context of COVID-19
Purpose
The construction industry is facing challenges not only for workers' mobility in the pandemic situation but also for Lean Construction (LC) practise in responding to the high-quality development during the post-pandemic. As such, this paper presents a construction workforce management framework based on LC to manage both the emergency goal in migrant worker management and the long-term goal in labour productivity improvement in China.
Design/methodology/approach
The framework is created based on the integrated culture and technology strategies of LC. A combination of qualitative and quantitative methods is taken to explore factors influencing the mobility of construction workers and to measure labour productivity improvement. The case study approach is adopted to demonstrate the framework application.
Findings
For method application, a time-and-motion study and Percent Plan Complete indicator are proposed to offer labour productivity measurements of “resources efficiency” and “flow efficiency”. Moreover, the case study provides an industry level solution for construction workforce management and Lean Construction culture shaping, as well as witnesses the LC culture and technology strategies alignment contributing to LC practise innovation.
Originality/value
Compared with previous studies which emphasised solely LC techniques rather than socio-technical system thinking, the proposed integration framework as well as implementation of “Worker's Home” and “Lean Work Package” management models in the COVID-19 pandemic contribute to new extensions of both the fundamental of knowledge and practise in LC
Nondipole Coulomb sub-barrier ionization dynamics and photon momentum sharing
The nondipole under-the-barrier dynamics of the electron during strong-field
tunneling ionization is investigated, examining the role of the Coulomb field
of the atomic core. The common analysis in the strong field approximation is
consequently generalised to include the leading light-front non-dipole Coulomb
corrections and demonstrates the counter-intuitive impact of the sub-barrier
Coulomb field. Despite its attractive nature, the sub-barrier Coulomb field
increases the photoelectron nondipole momentum shift along the laser
propagation direction, involving a strong dependence on the laser field. The
scaling of the effect with respect to the principal quantum number and angular
momentum of the bound state is found. With an improved light-front classical
Monte Carlo model, we disentangle sub-barrier and continuum Coulomb effects in
the nondipole regime. We demonstrate that the signature of Coulomb induced
sub-barrier effects can be identified in the asymptotic photoelectron momentum
distribution with state-of-the-art experimental techniques of mid-infrared
lasers.Comment: 6 pages, 4 figure
Origin of high energy enhancement of photoelectron spectra in tunneling ionization
Recently, in a strong Coulomb field regime of tunneling ionization an
unexpected large enhancement of photoelectron spectra due to the Coulomb field
of the atomic core has been identified by numerical solution of time-dependent
Schr\"odinger equation [Phys. Rev. Lett. \textbf{117}, 243003 (2016)] in the
upper energy range of the tunnel-ionized direct electrons. We investigate the
origin of the enhancement employing a classical theory with Monte Carlo
simulations of trajectories, and a quantum theory of Coulomb-corrected strong
field approximation based on the generalized eikonal approximation for the
continuum electron. Although the quantum effects at recollisions with a small
impact parameter yield an overall enhancement of the spectrum relative to the
classical prediction, the high energy enhancement itself is shown to have a
classical nature and is due to momentum space bunching of photoelectrons
released not far from the peak of the laser field. The bunching is caused by a
large and nonuniform, with respect to the ionization time, Coulomb momentum
transfer at the ionization tunnel exit
The effect of normal human serum on the mouse trypanosome Trypanosoma musculi in vitro and in vivo
Trypanosoma musculi, a common blood flagellate found in mice, is similar in morphology and life cycle to the rat trypanosome T. lewisi. Both species belong to the subgenus Herpetosoma, and as T. lewisi has recently been shown to be a zoonotic pathogen, there is concern that T. musculi could also be potentially infective to humans. To test this hypothesis, a well-established method, the normal human serum (NHS) incubation test, was carried out which distinguishes human and non-human infective trypanosomes. We found that T. musculi could grow in 0.31% NHS in vitro, and even kept their infectivity to mice after incubation with 10% NHS for 24 h. In in vivo experiments, T. musculi were only slightly affected by NHS injection, confirming that it was less sensitive to the NHS than T. b. brucei, but more sensitive than T. lewisi. This resistance probably does not rely on a restricted uptake of ApoL-1. Due to this partial resistance, we cannot definitively confirm that T. musculi has the potential for infection to humans. As resistance is less than that of T. lewisi, our data suggest that it is unlikely to be a zoonotic pathogen although we would advise caution in the case of immunocompromised people such as AIDS and cancer patients
Effect of Interlayer Coupling on Ultrafast Charge Transfer from Semiconducting Molecules to Mono- and Bilayer Graphene
Graphene is used as flexible electrodes in various optoelectronic devices. In these applications, ultrafast charge transfer from semiconducting light absorbers to graphene can impact the overall device performance. Here, we propose a mechanism in which the charge-transfer rate can be controlled by varying the number of graphene layers and their stacking. Using an organic semiconducting molecule as a light absorber, the charge-transfer rate to graphene is measured by using time-resolved photoemission spectroscopy. Compared to graphite, the charge transfer to monolayer graphene is about 2 times slower. Surprisingly, the charge transfer to A−B–stacked bilayer graphene is slower than that to both monolayer graphene and graphite. This anomalous behavior disappears when the two graphene layers are randomly stacked. The observation is explained by a charge-transfer model that accounts for the band-structure difference in mono- and bilayer graphene, which predicts that the charge-transfer rate depends nonintuitively on both the layer number and stacking of graphene
Prevalence and co-infection of Toxoplasma gondii and Neospora caninum in Apodemus sylvaticus in an area relatively free of cats
The protozoan parasite Toxoplasma gondii is prevalent worldwide and can infect a remarkably wide range of hosts despite
felids being the only definitive host. As cats play a major role in transmission to secondary mammalian hosts, the interaction
between cats and these hosts should be a major factor determining final prevalence in the secondary host. This study
investigates the prevalence of T. gondii in a natural population of Apodemus sylvaticus collected from an area with low cat
density (<2·5 cats/km2). A surprisingly high prevalence of 40·78% (95% CI: 34·07%–47·79%) was observed despite this.
A comparable level of prevalence was observed in a previously published study using the same approaches where a
prevalence of 59% (95% CI: 50·13%–67·87%) was observed in a natural population of Mus domesticus from an area with high
cat density (>500 cats/km2). Detection of infected foetuses frompregnant dams in both populations suggests that congenital
transmission may enable persistence of infection in the absence of cats. The prevalences of the related parasite, Neospora
caninum were found to be low in both populations (A. sylvaticus: 3·39% (95% CI: 0·12%–6·66%); M. domesticus: 3·08%
(95% CI: 0·11%–6·05%)). These results suggest that cat density may have a lower than expected effect on final prevalence in
these ecosystems
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